Many types of plugging devices for sealing against the inner wall of a pipe are known. Typically such plugging devices are used in the pipes of oil and/or gas wells or oil and/or gas production equipment, but they may also be used in other applications. Such plugging devices comprise a packer device provided circumferentially around the plugging device.
The packer device is in a retracted state during the transportation of the plugging device to the desired location in the pipe. At the desired location, the packer device is brought to an expanded state, for sealing against the inner wall of the pipe. The packer device comprises a packer body made of an elastic or ductile material in order to be brought between the retracted and the expanded states, and in order to seal against the inner wall of the pipe. The packer body is subjected to extrusion forces which may deform the packer body so much that it becomes damaged. In order to reduce the extrusion of the packer body, a supporting device or so-called backup ring is often incorporated into the packer body. The supporting device is also provided circumferentially around the plugging device.
One typical supporting device is a coil spring. However, when a spring is expanded due to the movement from the retracted state to the expanded state, the distance between each turn of the spring increases, allowing the ductile material of the packer body to extrude in between the openings between the respective turns. Moreover, the ductile material which has extruded into the openings between the respective turns will obstruct the spring to return to its retracted state when there is a need to retrieve the plugging device from the pipe. Hence, the plugging device may have a larger outer diameter during transportation out from the pipe than during transportation into the pipe, which may cause the plugging device to get stuck.
It is known to provide a core unit inside a spring, for example as in US 2006/0290066. Here the core unit comprises several interlinked elements, each having a first end connected to a second end of an adjacent element. Also here the distance between each element increases in the expanded state, allowing the material of the packer body to extrude between the openings of the spring and the opening between the elements. From U.S. Pat. No. 4,379,558 it is also known to provide a flat wire spring on the outside of the coiled spring, where the flat wire spring has overlapping contiguous elements forming a tubular encasement for the spring. It is difficult to provide the flat wire spring sufficiently strong, and the production of it is complex.
The object of the invention is to provide a packer device with a supporting device where the disadvantages above are avoided. One object of the present invention is to avoid the use of a coil spring in the supporting device.